Process for pulping



United States Patent 28, 39, 46, 46.02, 46.04, 46.06, 46.11, 46.17; 259/107, 108, 111; 259/162 (inquired CL.)

[56] References Cited UNITED STATES PATENTS 2,351,492 6/1944 Cowles 241/46. 1 7X 2,966,313 12/1960 Hughes... 241/4617 3,017,125 1/1962 Sherman 241/4617 Primary Examiner-Robert C. Riordon Assistant Examiner-Donald G. Kelly Attorneys-Pearson & Pearson ABSTRACT: Pulping process wherein an impeller with vanes is rotated in a tank containing water and waste paper such that a vortex is created to thus move the material within the tank. Vertical walls, located centrally of the length of the vanes, act,

when rotated, as flow intercepting barriers for a portion of the vortex flow to thus form a zone of turbulence for freeing the vanes of matting, plugging and stapling.

PATENTED 05m 5 I976 INVENTOR.

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Charles A. Johnson BY ATTORNEYS PROCESS FOR PULPING This is a division of application Ser. No. 603,904, filed Dec. 22, 1966, and now U.S. Pat. No. 3,432,107, issued Mar. 11, l969.

This invention relates to a novel and improved disintegrating and pulping process of the type used in the paper industry.

The type of pulper to which the invention relates may be either a side-rotor pulper or a bottom-rotor pulper, a singlerotor pulper or a dual-rotor pulper.

It has heretofore been proposed, as in U.S. Pat. No. 2,999,650, to Compagnano of Sept. 12, 1961, to provide a composite impeller in which there are a set of curved vanes for creating the usual vortical circulation in the tank, and a second set of spoon-shaped blades having upturned terminal tips for creating a secondary vortical circulation. In U.S. Pat. No. 2,966,3l3 to Hughes of Dec. 27, 1960, two sets of blades are also disclosed, each on a separate impeller, and each having triangularly upturned terminal tips for chewing up the stock. While the use of an abruptly upturned terminal tip on the vanes, disclosed in these patents, may well be useful for attrition purposes as in Hughes, or for creating a multiple vortical circulation pattern, as in Campagnano, such a configuration does not solve the problem of the plugging, matting or stapling of material on the vanes. It has been found that in all circulating vane structures presently used in waste paper, or broke, pulpers, despite the vortical circulation created by the impeller, the pulper gradually loses efficiency, due to an accumulation of material, especially on the leading edge of the vanes.

Applicants have discovered that a very substantial improvement in fiber stock handling characteristics of a pulper may be achieved by utilization of a pulping impeller comprising a plurality of identical, curved pulping vanes, which include, centrally of their length, an abrupt upward curvature to form an inwardly facing surface or wall, thereby forming a flow barrier and a zone of turbulence in the outwardly moving stream of stock. This novel design has been found to facilitate the handling of difficult-to-handle stock including paper waste, and to virtually eliminate plugging and stapling problems over a very wide range of pulping operations. Moreover, when these in wardly facing walls, or surfaces, which are preferably nearly normal to the plane in which the pulping impeller is operating, are somewhat remote from the impeller circumference, for example, set back at least percent of the distance from the periphery to the hub of the impeller, an especially beneficial circulating pattern featuring a relatively small vortex of less diameter than the impeller diameter is achieved.

Accordingly, it is an object of the invention to provide a novel pulping process which contributes efficient and continuous trouble-free operation to pulping operations.

It is another object of the invention to provide a process wherein a pulping impeller resists plugging, matting or stapling on the impeller vanes.

Another object of the invention is to provide a method for creating sufficient turbulence intermediate of the impeller to lift off adhered material on the vanes without unduly interfering with the normal vortical flow path of the pulper.

Other objects of the invention will be obvious from the claims the description of the drawings and from the drawings.

In this application and accompanying drawings, a preferred embodiment of the invention has been shown and described and alternatives and modifications thereof have been suggested, but it is to be understood that these are not intended to be exhaustive and that other changes and modifications can be made within the scope of the invention. These suggestions herein are selected and included for purposes of illustration in order that others skilled in the art will more fully understand the invention and the principles thereof and will be enabled to modify it and embody it in a variety of forms, each as may be best suited to the condition of a particular case. FIG. 1 is a sectional view in elevation of a pulper in which is mounted a pulper impeller according to the invention.

FIG. 2 is a plan view on line 2-2 of FIG. 1.

FIG. 3 is a perspective showing part of a pulper rotor of the invention with the novel pulping vane mounted thereon.

FIG. 4 is a view in elevation of a pulper vane according to the invention.

Referring to FIG. 1, it is seen that the pulp disintegrator, or pulper, 20, has a pulp container 21 with a flat, horizontal, central bottom portion 22, an upwardly sloping outer bottom portion 19, and an upstanding cylindrical wall 23. The pulp container 21 is adapted to receive a charge of water and paper stock material such as broke paper, waste paper, virgin lap pulp or the like. An arcuate sump 24 extends around the outer periphery of the container with a screen 25 in the bottom 22 and a drainpipe 26 all in a manner well known to the art for discharging the pulped stock. Impeller 30 is mounted in container 21 just above the bottom 22 to rotate in a horizontal plane on a vertical axis by means of central drive shaft 32. Drive shaft 32 is suitably journalled in bearings 34 mounted in bearing housing 35 fixed below central bottom aperture 36 of container 21. Commercially available O-rings and closure seals are used to prevent leakage in a manner known to the art and unnecessary for description in detail herein.

Impeller 30 includes a plurality of identical blades or pulping vanes 37, each of predetermined length, and having opposite and substantially parallel side faces 39 and 40. Vanes 37 are spaced on the flat diametrical face 27 of backplate 38 of impeller 30. Each vane 37 comprises an arcuate inner portion 41 which merges with a substantially straight outer portion 42. Arcuate portion 41 rises from proximate the central portion of backplate 38 to a first position centrally of the length of the vane and at about a constant l9 angle. Straight portion 42, however, starting approximately at the said first position at the juncture of portions 41, 42, rises sharply in rate of angular departure from backplate 38 to form an upwardly curved face which terminates in a vertical wall, or edge face,

'43, substantially normal to backplate 38 of impeller 30 and facing inward toward the center of the impeller at a second position centrally of the length of the vane. The upper edge face 44, of straight portion 42, is substantially parallel to backplate 38 of impeller 30 and vane 37 terminates in a downwardly sloping face 46, which extends beyond the edge of backplate 38.

Impeller 30 may include, along the outer periphery thereof, a series of projecting attrition blades 47, spaced around the periphery of the impeller and each at a predetermined angle from a radial line through the blade.

In operation, water and waste paper are supplied to container 21 and impeller 30 is caused to rotate by shaft 32. Pulping vanes 37 provide a recirculating action while attrition members 47 provide a shredding action on the waste paper pulp.

Whether the pulper is a side drive or bottom drive type, the vanes 37 create the usual vortex in which the material is continually moved around the side walls, or up the side walls, and is then drawn downwardly along the axis of the rotor impeller toward the centre and is then again centrifugally thrown outwardly toward the sidewalls. This conventional, and wellknown, vortical circulation is shown diagrammatically by the hollow-headed arrows and continues unchanged in the pulper of this invention, and is called the closed, vortical circulation path. The dislodging action of th the pulping vanes 37 of this invention is of a particularly advantageous nature in that a cylindrical zone of turbulence 49 appears to be formed, of less diameter than that of the closed vortical circulation path. The zone of turbulence is defined by the vertical walls 43 of the rotating vanes 37 which are believed to create a lifting force along the vanes capable of dislodging upwardly or forwardly any material tending to adhere to the leading edges of the blades. In 4, the zone of turbulence 49 is shown diagrammatically with solid-headed arrows. Stapling, matting and plugging are thus prevented, perhaps also because of the steep accelerating action of the rapidly rotating vertical walls 43 which imparts a high upward velocity to material coming in contact therewith. In a typical pulping operation the impeller will rotate at 400 to 500 r.p.m. At about 490 rpm. the tip would travel about 4000 feet per minute. At such speeds some types of waste paper, for example a piece of a paper pie plate, may

tend to hang up on the leading upper edge 50 of the upper face of one of the pulping vanes 37. This hanging up, or stapling, as it is known to the art, does not occur with the pulping vanes 37, the vertical walls 43, rotating unidirectionally at high speed, constituting identical barriers intermittently moving into and out of the flow path, intermediate of the vanes, to remove any material which might tend to adhere to the vanes.

Although a particular embodiment of the invention has been disclosed above in detail for illustrative purposes, it will be understood that variations or modifications of such disclosure, which lie within the scope of the appended claims are fully contemplated.

I claim: 1. A process for pulping waste paper by means of a vaned, circulating impeller rotating in a tank, comprising the steps of: vortically circulating the said paper in a closed path having a portion extending from the center of said impeller, along the vanes of said impeller to the walls of said tank; and unidirectionally rotating a plurality of identical barriers into and out of the said flow path portion, in an annular zone centrally of the length of the vanes of said impeller;

and

thereby disturbing said flow path sufficiently to dislodge any material tending to adhere to the leading faces, or edges, of said impeller vanes.

2. In a process for pulping fibrous paper stock material by means of a rotatable pulping impeller having pulping vanes mounted thereon, the improvement comprising the simultaneous steps of:

impacting and circulating said stock with energy imparted by motion of said pulping vanes, thereby causing said stock to flow in a direction generally away from the impeller beyond the periphery of said impeller in the plane of the impeller;

intercepting said stock flowing outwardly toward the periphery of said impeller, and causing a portion of said stock to be directed upwardly before reaching the periphery of said impeller; and

thereby forming a zone of turbulence intermediate of the length of the impeller vanes for freeing the vanes of matting, plugging and stapling. 

